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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

Space Shuttle Propulsion Systems Plume Modeling and Simulation for the Lift-Off Computational Fluid Dynamics Model

This paper details advances being made in the development of Reynolds-Averaged Navier-Stokes numerical simulation tools, models, and methods for the integrated Space Shuttle Vehicle at launch. The conceptual model and modeling approach described includes the development of multiple computational models to appropriately analyze the potential debris transport for critical debris sources at Lift-Off. The conceptual model described herein involves the integration of propulsion analysis for the nozzle/plume flow with the overall 3D vehicle flowfield at Lift-Off. Debris Transport Analyses are being performed using the Shuttle Lift-Off models to assess the risk to the vehicle from Lift-Off debris and appropriately prioritized mitigation of potential debris sources to continue to reduce vehicle risk. These integrated simulations are being used to evaluate plume-induced debris environments where the multi-plume interactions with the launch facility can potentially accelerate debris particles toward the vehicle.

Strutzenberg, L. L.↗
NASA NTRS1990

Identification of thermodynamically stable ceramic reinforcement materials for iron aluminide matrices

Aluminide-base intermetallic matrix composites are currently being considered as potential high-temperature materials. One of the key factors in the selection of a reinforcement material is its chemical stability in the matrix. In this study, chemical interactions between iron aluminides and several potential reinforcement materials, which include carbides, oxides, borides, and nitrides, are analyzed from thermodynamic considerations. Several chemically compatible reinforcement materials are identified for the iron aluminides with Al concentrations ranging from 40 to 50 at. pct.

Misra, Ajay K.↗
NASA NTRS2003

Interactions between neutrophils and macrophages promote macrophage killing of rat muscle cells in vitro

Current evidence indicates that the physiological functions of inflammatory cells are highly sensitive to their microenvironment, which is partially determined by the inflammatory cells and their potential targets. In the present investigation, interactions between neutrophils, macrophages and muscle cells that may influence muscle cell death are examined. Findings show that in the absence of macrophages, neutrophils kill muscle cells in vitro by superoxide-dependent mechanisms, and that low concentrations of nitric oxide (NO) protect against neutrophil-mediated killing. In the absence of neutrophils, macrophages kill muscle cells through a NO-dependent mechanism, and the presence of target muscle cells causes a three-fold increase in NO production by macrophages, with no change in the concentration of inducible nitric oxide synthase. Muscle cells that are co-cultured with both neutrophils and macrophages in proportions that are observed in injured muscle show cytotoxicity through a NO-dependent, superoxide-independent mechanism. Furthermore, the concentration of myeloid cells that is necessary for muscle killing is greatly reduced in assays that use mixed myeloid cell populations, rather than uniform populations of neutrophils or macrophages. These findings collectively show that the magnitude and mechanism of muscle cell killing by myeloid cells are modified by interactions between muscle cells and neutrophils, between muscle cells and macrophages and between macrophages and neutrophils.

Non-NASA Center↗
NASA NTRS1988

Transport properties for the oxygen system - O2, O, O(+), and e

The transport properties of the oxygen system, O2, O, O(+), and the electron, e, are calculated and their applications are discussed. The possible two-body interactions in the oxygen system are examined and the exponential repulsive potential is used to determine collision integrals for these interactions. Values are presented for the viscosity of the pure gases, the self-diffusion coefficient of the pure gases at 1 atm pressure, the translational thermal conductivity of the pure gases, and the internal thermal conductivity of O2.

Biolsi, Louis↗
NASA NTRS1967

Kinetic theory of dense-fluid mixtures. IV.

Kinetic prediction theory for viscosity, thermal conductivity and diffusivity of binary liquid mixtures composed of molecules interacting with square-well potential

VISCOUS FLUID↗
NASA NTRS1971

Supersonic jet noise suppression using coaxial flow interaction.

The scope of investigations conducted with coaxial interacting supersonic jet flows covers (1) acoustic measurements in both the far noise field and near noise field, (2) surveys of mean flow properties and fluctuating pressures, optical visualization of interacting jet flows, the associated flow and shock structure changes and the noise field, (3) the effects of different geometrical parameters of the coaxial nozzles, and (4) thrust measurements. It is shown that the flow interaction between two suitable controlled interacting coaxial supersonic axisymmetric jet flows results in substantial noise reduction based on equivalent thrust considerations. This flow interaction technique appears to be potentially an attractive approach for suppression of noise from supersonic jet exhausts.

Dosanjh, D. S.↗
NASA NTRS1974

Users guide for information retrieval using APL

A Programming Language (APL) is a precise, concise, and powerful computer programming language. Several features make APL useful to managers and other potential computer users. APL is interactive; therefore, the user can communicate with his program or data base in near real-time. This, coupled with the fact that APL has excellent debugging features, reduces program checkout time to minutes or hours rather than days or months. Of particular importance is the fact that APL can be utilized as a management science tool using such techniques as operations research, statistical analysis, and forecasting. The gap between the scientist and the manager could be narrowed by showing how APL can be used to do what the scientists and the manager each need to do, retrieve information. Sometimes, the information needs to be retrieved rapidly. In this case APL is ideally suited for this challenge.

Shapiro, A.↗
NASA NTRS1978

Modification of a very large thermal-vacuum test chamber for ionosphere and plasmasphere simulation

No large-volume chamber existed which could simulate the ion and electron environment of near-earth space. A very large thermal-vacuum chamber was modified to provide for the manipulation of the test volume magnetic field and for the generation and monitoring of plasma. Plasma densities of 1 million particles per cu cm were generated in the chamber where a variable magnetic flux density of up to 0.00015 T (1.5 gauss) was produced. Plasma temperature, density, composition, and visual effects were monitored, and plasma containment and control were investigated. Initial operation of the modified chamber demonstrated a capability satisfactory for a wide variety of experiments and hardware tests which require an interaction with the plasma environment. Potential for improving the quality of the simulation exists.

Pearson, O. L.↗
NASA NTRS1980

Field verification of lateral-torsional coupling effects on rotor instabilities in centrifugal compressors

Lateral and torsional vibration data obtained on a centrifugal compressor train which had shaft instabilities and gear failures is examined. The field data verifies that the stability of centrifugal compressors can be adversely affected by coincidence of torsional natural frequencies with lateral instability frequencies. The data also indicates that excitation energy from gear boxes can reduce stability margins if energy is transmitted either laterally or torsionally to the compressors. The lateral and torsional coupling mechanisms of shaft systems is discussed. The coupling mechanisms in a large industrial compressor train are documented and the potential effect on rotor stability is demonstrated. Guidelines are set forth to eliminate these potential problems by minimizing the interaction of torsional and lateral responses and their effect on rotor stability.

Wachel, J. C.↗
NASA NTRS1981

Development of a direct experimental test for any violation of the equivalence principle by the weak interaction

Violation of the equivalence principle by the weak interaction is tested. Any variation of the weak interaction coupling constant with gravitational potential, i.e., a spatial variation of the fundamental constants is investigated. The level of sensitivity required for such a measurement is estimated on the basis of the size of a change in the gravitational potential which is accessible. The alpha particle spectrum is analyzed, and the counting rate was improved by a factor of approximately 100.

Parker, P. D. M.↗
NASA NTRS1981

On rotational forces in the solar wind

Solar rotational forces affecting the flow of minor ions in the solar wind are considered as corotating with the sun. Cold, noninteracting charged particles in the magnetic and gravitational fields of the sun rotate with the angular velocity of the sun, and calculations of lowest bulk order velocities show that differences in particle velocities decrease with increasing distance from the sun. A centrifugal potential in the corotating frame implies that ion motion is independent of protons, with velocities determined by the potential, which monotonically decreases without limit. The potential dominates the initial kinetic energy of the particles, and the equality of velocities within the potential is not due to interactions between particles as claimed by Mackenzie et al. (1979).

Hollweg, J. V.↗
NASA NTRS1980

A comparison of secondary craters on the moon, Mercury, and Mars

The present investigation is concerned with the distribution of secondary crater sizes and shapes and the relation of these distributions to inferred Martian lithology and ballistic history. Differences in secondary-crater size/range distributions around unmodified craters can be attributed to differences in gravitational potential, lithologic properties, and atmospheric interactions. Wide variations found in secondary crater populations around medium-size (5-50 km) Martian craters can be interpreted as effects of contrasting target lithologies. Extensive secondary cratering and elongate secondaries of Crater I in Chryse Planitia are consistent with a competent lithology of basaltic plains, as inferred from various photogeologic studies. The relatively few large secondaries around Arandas, and their high circularity, are consistent with a lithology exhibiting low yield strength, as inferred for the fractured plains.

Schultz, P. H.↗
NASA NTRS1983

Pyroelectric conversion in space: A conceptual design study

Pyroelectric conversion is potentially a very lightweight means of providing electrical power generation in space. Two conceptualized systems approaches for the direct conversion of heat (from sunlight) into electrical energy using the pyroelectric effect of a new class of polar polymers were evaluated. Both of the approaches involved large area thin sheets of plastic which are thermally cycled by radiative input and output of thermal energy. The systems studied are expected to eventually achieve efficiencies of the order of 8% and may deliver as much as one half kilowatt per kilogram. In addition to potentially very high specific power, the pyroelectric conversion approaches outlined appear to offer low cost per watt in the form of an easily deployed, flexible, strong, electrically ""self-healing'', and high voltage sheet. This study assessed several potential problems such as plasma interactions and radiation degradation and suggests approaches to overcome them. The fundamental technological issues for space pyroelectric conversion are: (1) demonstration of the conversion cycle with the proposed class of polymers, (2) achievement of improved dielectric strength of the material, (3) demonstration of acceptable plasma power losses for low altitude, and (4) establishment of reasonable lifetime for the pyroelectric material in the space environment. Recommendations include an experimental demonstration of the pyroelectric conversion cycle followed by studies to improve the dielectric strength of the polymer and basic studies to discover additional pyroelectric materials.

Olsen, R. B.↗
NASA NTRS1984

A Concept for the Processing and Display of Thematic Mapper Data

Multispectral information can best be accessed and evaluated through digital interactive image processing techniques. The potential user community, however, has not reached the level where image processing is being used routinely as a standard tool. Therefore, for the time being, special effort must be put into development of strategies that will guarantee optimal utilization of the spectral information contained in remote sensing data acquired under the varying conditions affecting each scene. The Thematic Mapper system provides spectral information in seven carefully selected spectral bands, covering the visible, near IR, short-wave IR and thermal IR region of the electromagntic spectrum. The challenge is to devise the best approach for presenting this complex spectral information in a pictorial format which can be understood and accepted as a standard by the growing user community.

Haydn, R.↗
NASA NTRS1990

Optimizing the use of remotely sensed atmospheric data through four-dimensional data assimilation

Results with the GLA interactive forecast-retrieval-assimilation system, which directly uses satellite radiance data in the assimilation cycle, are presented. Forecasts made from initial conditions derived with this system are shown to be more skillful than those whose initial conditions came from a comparable assimilation using statistically based temperature soundings, or ones using no sounding data at all. Examples are also given of additional parameters which are produced through the physical inversion of the satellite radiance data during the interactive assimilation cycle. These are potentially useful for analysis purposes.

Pfaendtner, J.↗